This project focuses on the chemical, immunological and biological properties of human chorionic gonadotopin (hCG) in tissues and body fluids. Previous studies have demonstrated the presence of an hCG-like substance (hCG') in the human pituitary gland and urine of normal subjects and women employing contraceptive measures. The use of gel-HPLC followed by specific radioimmunoassays of column effluents has revealed that the hCG' from urine of normal women is smaller than pregnancy hCG, possibly due to incomplete glycosylation of the molecule in the pituitary gland. The hCG' from urine of women bearing an intra-uterine device resembles pregnancy hCG, consistent with the possibility that a fertilized ovum may have briefly implanted. A high pressure liquid chromatofocusing method has also been applied to the separation of hCG and its derivatives. Further characterization of effluents by specific radioimmuno-assays permits qualitative and quantitative determination of the intact, desialylated and deglycosylated hCG and their subunits. The results from these combined studies have provided better understanding of the absence of hormonal responses in certain subjects with elevated levels of immunologically assayed hCG in biological fluids. We have identified by an immunocytochemical method an intermediate form of hCG-secreting cell, distinct from cyto- and syncytiotrophoblast, in human placental tissues of the first trimester. This cell is believed to play a role in implantation and in the establishment of the utero-placental circulation. Previously, we have reported that dimeric [D-Ala2, Leu5] and [D-Ala,2des-Leu5] enkephalins cross-linked at the carboxyl-terminus by methylene chains of various length are highly Delta-selective with increasing potency as compared to their respective monomers. In addition to these two series of enkephalin dimers, two alkylamidated monomers of such sequences have been synthesized. The analyses of Delta -and Mu-activities of alkylamidated peptides in parallel to their bivalent analogs have revealed that bivalency is important for the increase of the affinity and Delta-selectivity of these derivatives.